code: def test_survdiff_basic():
      # Constants taken from R, code above
      ti = np.concatenate((ti1, ti2))
      st = np.concatenate((st1, st2))
      groups = np.ones(len(ti))
      groups[0 : len(ti1)] = 0
      z, p = survdiff(ti, st, groups)
      assert_allclose(z, 2.14673, atol=1e-4, rtol=1e-4)
      assert_allclose(p, 0.14287, atol=1e-4, rtol=1e-4)
  
imports: import os
  import numpy
  from statsmodels.duration.survfunc import SurvfuncRight, survdiff, plot_survfunc, CumIncidenceRight
  from numpy.testing import assert_allclose
  import pandas
  import pytest
label_desc: Use image node_id 4 for calling a global function with example usage: test_survdiff_basic() without return types